<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  
  <div id="app">
    <h2>当前计数: {{counter}}</h2>
    <button @click="increment">+1</button>
  </div>

  <script src="./lib/vue.js"></script>
  <script>

    console.log(this)

    const app = Vue.createApp({
      data: function() {
        return {
          counter: 0
        }
      },

      // methods: option api
      methods: {
        increment: function() {
          this.counter++
        },
        // 强调: methods中函数不能写成箭头函数
        // increment: () => {
        //   console.log(this)
        // }
      }
    })

    app.mount("#app")
  </script>
</body>
</html>